First, TimedMediaHandler isn't normalizing dimensions for audio files, which means that the height=-1 being passed to indicate "don't limit by height" is being misinterpreted.

And second, TimedMediaHandler is using an incorrect calculation when the height is the limiting factor on the thumbnail dimensions, leading to the width of 1913. The same happens if you pass something like iiurlwidth=220&iiurlheight=10.

Since both of these are in TimedMediaHandler, I'm going to reassign this there. I'll also submit a patch momentarily.